Upgrade metrics-lib to Debian buster libraries

I already updated most libraries in metrics-base and metrics-lib master to Debian buster for #31172 (moved) to fix the Jenkins build. We should review those changes anyway, which is why I'm creating this ticket. Commits are:

e12ba96 in metrics-base.git and
453a6f5 in metrics-lib.git.

We'll also have to resolve an issue with the latest Checkstyle version 8.15 ("Unable to create Root Module"). I don't really know how to start debugging this, so I'll leave this for others for now.

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